No we don’t and we should be honest about that.
(1) God exists.
(2) [Atheist makes counterarguments.]
(3) I will pray for you.
I have heard this one from many apologists. They have some kind of argument that if they could only get the atheist to understand it, they would have to conclude that God does indeed exist. They range from the Kalam argument to the Efficient Causality argument to the argument from Design to the Transcendental argument and many, many more. Some are simple and some are complex and all of these have merit and are good to reason through but in the end all have flaws that are not going to convince an atheist who trusts science to discover truth.
If this was true and we can prove God exists to atheists, then why are atheists not convinced? Atheists are very diverse in their beliefs. I don’t want to put them all in one camp but in my experience the ones that will discuss theology honestly with Christians are very logical, have good critical thinking skills and have put their trust in science as the best way to find truth. In the end Christians do not have a rational explanation as to why we believe.
The Christian faith is an irrational faith. We cannot in any way explain our belief in talking donkeys, people living in fish, people transported to different places instantly or even explain our belief in God in any rational way. So let’s just stop pretending we can.
So why do we Christians believe in God? Well, the answer is that God has made us all to believe. Now I am going to presuppose that the Bible is true just like atheists presuppose science is the best way to find truth.
Romans chapter one is a favorite verse from presuppositionalists who believe that all people believe in God but some such as atheists deny it because of their sin. Here’s what it says:
For the wrath of God is revealed from heaven against all ungodliness and unrighteousness of men, who by their unrighteousness suppress the truth. For what can be known about God is plain to them, because God has shown it to them. For his invisible attributes, namely, his eternal power and divine nature, have been clearly perceived, ever since the creation of the world, in the things that have been made. So they are without excuse. For although they knew God, they did not honor him as God or give thanks to him, but they became futile in their thinking, and their foolish hearts were darkened. Claiming to be wise, they became fools, and exchanged the glory of the mortal God for images resembling mortal man and birds and animals and creeping things. ~ Romans 1:18-23 ESV
Now I 100% agree with this verse. We all know God does exist. The presuppositionalist will beat up the atheist with this verse without any explanation or understanding that from the atheist point of view they do not believe. The atheist will and with good reason be offended because you are telling them what they think when they think differently without any proof that they would require. The Christian then puts the blame on the atheist for not believing in God because of their sin and that is in the wrong place. The blame should rightfully be put at Gods feet so to speak.
Romans goes on to say:
And since they did not see fit to acknowledge God, God gave them up to a debased mind to do what ought not to be done. ~ Romans 1:28 ESV
Our faith is a free gift from God (Romans 5:1, 12:3) and is not rational but supernatural. Jesus is the author of our faith (Hebrews 12;2) and God is responsible for how much faith we get as well (Romans 14:1) so we cannot blame the atheist for their lack of faith. We can take it to God himself.
In the end it is God that gives faith and does not give faith for His purposes. We cannot prove God exists only god can prove He does indeed exist to people. One reason I know God exists is that I have faith in the first place and that is not a rational argument that any thinking atheist would accept.
So what should Christians do? We should preach the Gospel to everyone including atheists and trust that God knows what He is doing. Faith is given to us by God through hearing the Gospel not by scientific proofs or logical arguments.